1. Technical Field
The present invention relates to a resist film, and more particularly, to a resist film used for forming a circuit wiring of a printed circuit board.
2. Description of the Related Art
A resist is generally used for forming a circuit wiring in a printed circuit board. For example, describing a MSAP method which is one of methods of forming a circuit, a seed layer is deposited on one surface of a substrate and a resist is then attached thereto, which in turn is subjected to exposure and development processes to thereby form a resist pattern. Next, the seed layer is electroplated by a lead wire to thereby deposit a metal between the resist patterns, and the seed layer exposed to the outside after removing the resist is etched to thereby form the circuit wiring (see Korean Patent Laid-Open Publication No. 10-2006-0042015).
Meanwhile, the resist may be included in the outermost layer of the substrate to thereby serve to protect the substrate in addition to forming the circuit. In this case, in order to connect between elements such as a pad, a semiconductor chip, and the like formed on the outermost layer of the substrate, an opening part exposing the pad of the substrate needs to be formed in the resist, which is also performed by the exposure and development processes.
As such, the pattern or the opening part is formed by performing the exposure and development processes on the resist. In this case, at the time of the development process, a developing solution is directly sprayed to the resist. In this case, the developing solution physically hits a surface of the resist with a spray pressure. As a result, an undercut phenomenon in which a lower portion of the pattern which is insufficiently cured is separated may occur. This may cause a pattern lifting problem.
In addition, an abrasion such as a scratch, a tear, or the like may be formed on a pattern surface due to the cutting phenomenon of the surface of the pattern and an appearance defect in which a variety of filler contained in the resist is protruded to the outside may occur. Even if the scratch is small, in the case in which high pressure is applied to the substrate when an element is mounted on the substrate, a size of the scratch is gradually increased, thereby causing damage to the whole resist.
Meanwhile, the resist is generally composed using a polymer having a carboxyl group (—COOH) as a functional group in order to improve hydrophilic property. However, in the case in which carboxyl group (—COOH) molecules on the resist surface are separated due to the physical hit by the spray pressure, the resist surface is changed to be hydrophobic. As a result, surface energy of the resist may be decreased, thereby deteriorating flowability of a resin in an underfill process when the element is mounted on the substrate.